Problem: Constraints

* H is an integer between 2 and 50 (inclusive).
* W is an integer between 2 and 50 (inclusive).
* s_{i, j} is `.` or `#` (1 \leq i \leq H, 1 \leq j \leq W).
* s_{1, 1} and s_{H, W} are `.`.

Input

Input is given from Standard Input in the following format:


H W
s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}
s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}
:   :
s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}


Output

Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.

Examples

Input

3 3
..#
#..
...


Output

2


Input

3 3
..#
..
...


Output

2


Input

10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................


Output

209

Solution (in PYTHON3):

Solution:
from collections import deque
m=[[1,0],[-1,0],[0,1],[0,-1]]
h,w=map(int,input().split())
l=list()
l.append('#'*(w+2))
p=0
for i in range(h):
    j=input()
    p+=j.count('#')
    l.append('#'+j+'#')
l.append('#'*(w+2))
q=deque([[1,1]])
s=[[-1 for j in i] for i in l]
s[1][1]=1
while len(q)>0:
    x,y=q.popleft()
    for i,j in m:
        if l[x+i][y+j]=='.' and s[x+i][y+j]==-1:
            q.append([x+i,y+j])
            s[x+i][y+j]=s[x][y]+1
    if s[h][w]!=-1:
        break
if s[h][w]!=-1:
  print(h*w-p-s[h][w]) 
else:
  print(-1)